First off I had a 4 sundown nightshade v1 15s and 1 of them started doing this with no obvious reason why. It was the one I had been using by itself while the build was in progress. Now I got a smaller car. I've been using the same crappy amp as I did when I used the single nsv1 (hifonics bxi2008 not a great amp I know) but I've been running this hdc3 18 aluminum coil since it was new and its only been like 2 months but today thanks guysor yesterday it started rattling especially on low notes. No tinsel slap. It has direct leads but I looked anyway. All visible suspension is in tact. Same thing happened w the ns as I said. Now I'm wonering if anyone has any insight id appreciate itif you could help me out. Both coils work. Havnt tested the loads. The box is tiny for it. Its like 5 cubes before sub displacement. Its temporary and it gets loud anyway but I have it in the trunk of a grand am for now so don't pick on me too much. Also...if I'm a bit incoherent its because I'm drunk lol thanks guys.